The present invention relates to a flux-containing composition comprising a metallic powder for brazing (also referred to as a brazing powder) useful for brazing aluminum materials to be jointed. The term xe2x80x9caluminumxe2x80x9d referred to herein includes pure aluminum and its alloys otherwise specifically described.
Further, the present invention relates to an undried film resulting from a composition for brazing useful for brazing aluminum materials to be jointed and a brazing method through the undried film.
In order to braze aluminum, brazing sheets have been often used. The brazing sheets used comprise cores made of alloys such as 3003 alloy, 3N03 alloy or the like clad with brazing materials such as 4343 alloy or 4045 alloy on either or both surfaces thereof. These numbers of four ciphers are as specified in JIS. Since such a clad brazing material is indispensably applied to areas other than those to be brazed, a cost of a final product is increased. And, a thickness of a clad material is limited by problems in the preparation of the clad material. The minimum thickness is about 60 xcexcm since it is very difficult to industrially prepare a thinner clad material. Even prepared, the resultant clad material has a skin with an uneven thickness and therefore, its qualities and properties are not constant.
When brazing sheets are brazed, fluxes are essential. One type is fluxes to be applied to areas to be brazed immediately before brazing. However, it is difficult that most of the fluxes are completely dried due to their compositions. Even if dried, the flux is readily peeled off and dropped so that it is impossible to store and transport for a long period before brazing. And, processing, assembly and the like are also impossible.
Generally, a suspension comprising a flux mixed with water is applied by spraying or using any other means and dried before a brazing operation (step). However, the application of the suspension may scatter the flux over undesirable areas, which is not preferable for operating environment and health. On the other hand, when the drying before the brazing step is incomplete, water is left in a brazed area which may lower a brazing property and produce defects in the brazed area. Moreover, when water is contained as a medium, a flux is not well adhered to a brazing sheet. And, it is not evenly coated. Excess flux in areas to which much amounts of the flux are adhered may form gray or white stains, while areas to which less amounts of the flux are adhered may have an insufficient brazing property.
For overcoming the problems mentioned above, a method comprising adding a water soluble resin as a binder was proposed as disclosed in JP 6285682A. This method gives a final product with a commercially unattractive appearance since the reaction of the binder with the flux during brazing makes brazed areas dark. Even if the water soluble resin was used, the resultant film was readily peeled off and dropped due to its poor film-forming property. Thus, processing and assembly after the application of the flux were substantially impossible. The use of the resin of solvent type is not suitable for industrial preparation since the change in color of brazed areas and the production of cracks may occur irrespective of drying of the resultant film.
Recently, a brazing method in which an area to be brazed of an aluminum material is coated with a mixture of an aluminum-silicon brazing powder and a flux in place of the use of a brazing sheet has been proposed. This method solves the problem of costs, but the other problems mentioned above cannot be solved thereby.
The present inventors completed the present invention via repeated study. Thus, the present invention is directed to a composition, a film and a method as defined by the preferable embodiments A to D below.
A1. A flux-containing composition for brazing aluminum comprising:
a) 10 to 70% by weight of a metallic powder for brazing,
b) 2 to 50% by weight of a fluoride flux, and
c) 1 to 15% by weight of at least one binder selected from the group consisting of an alkyd resin, a mixture of an alkyd resin and a butyl rubber, a mixture of an alkyd resin and a petroleum resin, a mixture of an alkyd resin, a butyl rubber and a petroleum resin, a mixture of an acrylic resin and a butyl rubber, a mixture of an acrylic resin and a petroleum resin and a mixture of an acrylic resin, a butyl rubber and a petroleum resin,
the balance being substantially an organic solvent provided that the total is not more than 100% by weight.
A2. A flux-containing composition for brazing aluminum as defined in (A1) wherein the metallic powder for brazing is a powdery mixture of a pure aluminum powder and a silicon powder.
A3. A flux-containing composition for brazing aluminum as defined in (A1) wherein the metallic powder for brazing is a powdery mixture of a pure aluminum powder, a silicon powder and a zinc powder.
A4. A flux-containing composition for brazing aluminum as defined in (A1) which comprises a coupling agent.
A5. A film obtained by coating at least a part of a surface of an aluminum material with a paste composition as defined in (A1) to (A4) and then drying.
A6. An aluminum material coated with a paste composition as defined in (A1) to (A4) onto at least a part of its surface and then dried.
A7. A method of brazing an aluminum material comprising:
coating at least a part of a surface of the aluminum material with a paste composition for brazing aluminum comprising a) 10 to 70% by weight of a metallic powder for brazing, b) 2 to 50% by weight of a fluoride flux, and c) 1 to 15% by weight of at least one binder selected from the group consisting of an alkyd resin, a mixture of an alkyd resin and a butyl rubber, a mixture of an alkyd resin and a petroleum resin, a mixture of an alkyd resin, a butyl rubber and a petroleum resin, a mixture of an acrylic resin and a butyl rubber, a mixture of an acrylic resin and a petroleum resin and a mixture of an acrylic resin, a butyl rubber and a petroleum resin, the balance being substantially an organic solvent provided that the total is not more than 100% by weight;
drying; and then
brazing any other aluminum material.
B1. A flux-containing composition for brazing aluminum comprising a) 10 to 50% by weight of a fluoride flux and b) 0.1 to 10% by weight of at least one binder selected from the group consisting of a polyethylene resin, a mixture of a butyl rubber and a polyethylene resin, a mixture of a petroleum resin and a polyethylene resin and a mixture of a butyl rubber, a petroleum resin and a polyethylene resin,
the balance being substantially an organic resin provided that the total is not more than 100% by weight.
B2. A flux-containing composition for brazing aluminum as defined in (B1) wherein the fluoride flux is at least one selected from the group consisting of AlF3-KF, KAlF4-K3AlF6, K3AlF6 and KAlF4.
B3. A film obtained by coating at least a part of a surface of an aluminum brazing sheet with a flux composition as defined in (B1) or (B2) and then drying.
B4. An undried film obtained by coating at least a part of a surface of an aluminum brazing sheet with a flux composition as defined in (B1) or (B2).
B5. An aluminum brazing sheet having a film as defined in (B3) or (B4) onto at least a part of its surface.
B6. A method of brazing an aluminum material comprising:
coating at least a part of a surface of an aluminum brazing sheet with a flux composition for brazing aluminum comprising a) 10 to 50% by weight of a fluoride flux and b) 0.1 to 10% by weight of at least one binder selected from the group consisting of a polyethylene resin, a mixture of a butyl rubber and a polyethylene resin, a mixture of a petroleum resin and a polyethylene resin and a mixture of a butyl rubber, a petroleum resin and a polyethylene resin, the balance being substantially an organic resin provided that the total is not more than 100% by weight;
drying; and then
brazing any other aluminum material.
B7. A method of brazing as defined in (B6) which is conducted in a close or open condition.
B8. A method of brazing an aluminum material comprising:
coating at least a part of a surface of an aluminum brazing sheet with a flux composition for brazing aluminum comprising a) 10 to 50% by weight of a fluoride flux and b) 0.1 to 10% by weight of at least one binder selected from the group consisting of a polyethylene resin, a mixture of a butyl rubber and a polyethylene resin, a mixture of a petroleum resin and a polyethylene resin and a mixture of a butyl rubber, a petroleum resin and a polyethylene resin, the balance being substantially an organic resin provided that the total is not more than 100% by weight; and then
brazing any other aluminum material through the resultant undried film.
B9. A method of brazing as defined in (B8) which is conducted in a close or open condition.
C1. A flux-containing composition for brazing aluminum comprising:
(a) 10 to 70% by weight of an alloy powder for brazing,
(b) 2 to 50% by weight of a fluoride flux, and
(c) 1 to 15% by weight of at least one binder selected from the group consisting of an alkyd resin, a mixture of an alkyd resin and a butyl rubber, a mixture of an alkyd resin and a petroleum resin, a mixture of an alkyd resin, a butyl rubber and a petroleum resin, a mixture of an acrylic resin and a butyl rubber, a mixture of an acrylic resin and a petroleum resin and a mixture of an acrylic resin, a butyl rubber and a petroleum resin,
the balance being substantially an organic solvent provided that the total is not more than 100% by weight.
C2. A paste composition for brazing aluminum as defined in (C1) wherein the alloy powder for brazing is an aluminum-silicon alloy powder of an average particle size ranging from 2 to 100 xcexcm.
C3. A flux-containing composition for brazing aluminum as defined in (C1) wherein the alloy powder for brazing is an aluminum-silicon-zinc alloy powder of an average particle size ranging from 2 to 100 xcexcm.
C4. A flux-containing composition for brazing aluminum comprising:
(a) 10 to 70% by weight of a powdery mixture comprising an aluminum-silicon alloy powder of an average particle size ranging from 2 to 100 xcexcm and a zinc powder,
(b) 2 to 50% by weight of a fluoride flux, and
(c) 1 to 15% by weight of at least one binder selected from the group consisting of an alkyd resin, a mixture of an alkyd resin and a butyl rubber, a mixture of an alkyd resin and a petroleum resin, a mixture of an alkyd resin, a butyl rubber and a petroleum resin, a mixture of an acrylic resin and a butyl rubber, a mixture of an acrylic resin and a petroleum resin and a mixture of an acrylic resin, a butyl rubber and a petroleum resin,
the balance being substantially an organic solvent provided that the total is not more than 100% by weight.
C5. A flux-containing composition for brazing aluminum as defined in any one of (C1) to (C4) which comprises a coupling agent.
C6. A film obtained by coating at least a part of a surface of an aluminum material with a paste composition as defined in any one of (C1) to (C5) and then drying.
C7. An aluminum material coated with a paste composition as defined in any one of (C1) to (C5) onto at least a part of its surface and then dried.
C8. A method of brazing an aluminum material comprising:
coating at least a part of a surface of the aluminum material with a paste composition for brazing aluminum comprising (a) 10 to 70% by weight of an alloy powder for brazing or a powdery mixture of an alloy powder for brazing and a zinc powder, (b) 2 to 50% by weight of a fluoride flux, and (c) 1 to 15% by weight of at least one binder selected from the group consisting of an alkyd resin, a mixture of an alkyd resin and a butyl rubber, a mixture of an alkyd resin and a petroleum resin, a mixture of an alkyd resin, a butyl rubber and a petroleum resin, a mixture of an acrylic resin and a butyl rubber, a mixture of an acrylic resin and a petroleum resin and a mixture of an acrylic resin, a butyl rubber and a petroleum resin, the balance being substantially an organic solvent provided that the total is not more than 100% by weight;
drying; and then
brazing any other aluminum material.
D1. An undried film for brazing obtained by coating at least a part of an aluminum material with a composition comprising
a) 10 to 70% by weight of a metallic powder for brazing, b) 2 to 70% by weight of a fluoride flux, and c) 0.1 to 10 % by weight of at least one binder selected from the group consisting of a butyl rubber, a petroleum resin and a polyethylene resin,
the balance being substantially an organic solvent provided that the total is not more than 100% by weight.
D2. An undried film for brazing as defined in (D1) wherein the metallic powder for brazing is a powdery mixture of a pure aluminum powder of an average particle size ranging from 1 xcexcm to 10 xcexcm and a silicon powder of an average particle ranging from 0.1 xcexcm to 10 xcexcm.
D3. An undried film for brazing as defined (D1) wherein the metallic powder for brazing is a powdery mixture of a pure aluminum powder of an average particle size ranging from 1 xcexcm to 10 xcexcm, a silicon powder of an average particle size ranging from 0.1 xcexcm to 10 xcexcm and a zinc powder of an average particle size ranging from 0.1 xcexcm to 10 xcexcm.
D4. An undried film for brazing as defined in (D1) wherein the metallic powder for brazing is an aluminum-silicon alloy powder of an average particle size ranging from 2 to 100 xcexcm.
D5. An undried film for brazing as defined in (D1) wherein the metallic powder for brazing comprises an aluminum-silicon alloy powder of an average particle size ranging from 2 to 100 xcexcm and a zinc powder of an average particle size ranging from 0.1 xcexcm to 10 xcexcm.
D6. An undried film for brazing as defined in (D1) wherein the metallic powder for brazing comprises an aluminum-silicon-zinc alloy powder of an average particle size ranging from 2 to 100 xcexcm.
D7. An aluminum material having an undried film for brazing as defined in any one of (D1) to (D6).
D8. A method of brazing an aluminum material comprising:
coating at least a part of a surface of an aluminum material with a composition comprising a) 10 to 70% by weight of a metallic powder for brazing, b) 2 to 70% by weight of a fluoride flux, and c) 0.1 to 10% by weight of at least one binder selected from the group consisting of a butyl rubber, a petroleum resin and a polyethylene resin, the balance being substantially an organic solvent provided that the total is not more than 100% by weight; and then
brazing any other aluminum material through the resultant undried film.
D9. A method as defined in (D8) wherein the brazing is conducted in a close or open condition.